Apparatus for supplying or draining a fluid to or from the marginal portion of a flat fuel cell electrode and an electrode element and a fuel cell provided with such an apparatus

Abstract

 Apparatus for supplying or draining a fluid to or from a marginal portion of a flat fuel cell electrode, consisting of a supply or drainage device for the fluid, which is connected with a spacious collecting channel (5) which runs substantially parallel to the marginal portion of the fuel cell electrode and which is connected with a number of substantially equidistantly spaced points of this marginal portion via micro-channels (4), these micro-channels having substantially identical dimensions and a width b that is smaller than their depth d. Preferably b/d is at most 0.9, and H/h is larger than 3, H and h being the hydraulic diameters of, respectively, the collecting channel (5) and the micro-channels (4).

Description

[0001] The invention relates to an apparatus for supplying or draining a fluid to or from the marginal portion of a flat fuel cell electrode, which electrode is mounted in a frame thus forming with this frame and the apparatus an electrode-element, which apparatus consists of at least a supply or drainage device for the fluid.

[0002] Such an apparatus is known from United States patent specification 3,901,731. This known apparatus consists of a number of supply or drainage channels for electrolyte which are connected, via a number of micro-channels running in a plane parallel to the longitudinal plane of a plastic frame, in which frame a flat electrode is mounted and which frame incorporates the apparatus, and a distribution area having a rather complicated structure, with a marginal portion of the flat electrode. The total of electrode, plastic frame and apparatus from an electrode-element. The micro-channels are open at the upper side, which side is situated in one of the two outer planes of the plastic frame that are parallel to the longitudinal plane of said plastic frame, when the electrode-element is not assembled, e.g. with other elements in an electrode-stack or a battery. According to this US patent specification the micro-channels vary in length, width b and depth d, b/d being at least 1.5. A high b/d has as a result that the hydraulic diameter of the micro-channel will to a large extent become dependent upon the value of d. Small variations of d, which are not identical for the various micro-channels, e.g. as a result of the penetration of slight amounts of sealing material when the channel tops are sealed, e.g. when the electrode-element is attached to an other element to form a battery, thus have a very large influence on the distribution of the fluid among the various channels. This renders it practically impossible to manufacture a fuel cell consisting of a stack of electrode elements that is provided with such apparatuses according to US patent specification 3,901,731 and in which the required fluids are uniformly supplied to and drained from all electrodes.

[0003] An apparatus according to the invention does not exhibit this disadvantage. Such an apparatus for supplying or draining a fluid to the marginal portion of a flat fuel cell electrode, which electrode is mounted in a frame thus forming with this frame and the apparatus an electrode-element, which apparatus consists of at least a supply or drainage device for the fluid, is characterized in that said supply or drainage device is connected with a spacious collecting channel which runs in a plane parallel to the longitudinal plane of the frame and runs substantially parallel to said marginal portion of the fuel cell electrode and which is connected with a number of substantially equidistantly spaced points of this marginal portion via micro-channels, which micro-channels run in a plane parallel to the longitudinal plane of the frame and are open at the upper side, which side is situated in one of the two outer planes of the frame that are parallel to the longitudinal plane of the said frame, when the electrode-element is not assembled and have substantially identical dimensions and a width b that is smaller than their depth d. The b/d therefore preferably is at most 0.9, more in particular at most 0.5.

[0004] It is remarked that from the US patent specification 3,717,505 an apparatus is known for supplying or draining a fluid to the marginal portion of a fuel cell electrode, that consists of a supply or drainage device for the fluid, which device is connected with a spacious collecting channel which runs substantially parallel to the said margi- _nal portion of the fuel cell electrode and which is connected with a number of substantially equidistantly spaced points of this marginal portion via connecting channels. However, these connecting channels have a round cross section and are comprised totally in the material of the frame that surrounds the electrode. They do not have an open upper side situated in one of the two outer planes of said frame that are parallel to the longitudinal plane of said frame.

[0005] The collecting channel has a hydraulic diameter H that is much larger than the hydraulic diameter h of the micro-channels. The ratio between the hydraulic diameter H of the collecting channel and the hydraulic diameter h of the micro-channels preferably is larger than 3, more in particular larger than 5.

[0006] Figure 1 describes an embodiment of an apparatus according to the invention. Supply channel 3 is connected with collecting channel 5 via connection 6. Via the plurality of micro-channels 4 collecting channel 5 is connected with a flat electrode 1. This electrode is mounted in plastic frame 2. The distance between points A and B, B and C, C and D etc. are substantially equal.

[0007] Figure 2 shows a cross section along line A-A in figure 1 (not exactly to scale) across two micro-channels 4. b is smaller than d.

[0008] The invention also relates to an electrode-element consisting of a flat electrode in a frame, which frame is preferably made of thermoplastic material and provided with one or more apparatuses according to the invention for the supply and/or discharge of one or more fluids to and/or from one or more marginal portions of the flat electrode.

[0009] The invention further relates to a fuel cell or battery consisting of a stack of elements, one or more of which are electrode elements as referred to.

Claims

₁. Apparatus for supplying or draining a fluid to or from a marginal portion of a flat fuel cell electrode, which electrode is mounted in a frame thus forming with this frame and apparatus an electrode-element, which apparatus consists of at least a supply or drainage device for the fluid, characterized in that said supply or drainage device is connected with a spacious collecting channel which runs in a plane parallel to the longitudinal plane of the frame and runs substantially parallel to said marginal portion of the fuel cell electrode and which is connected with a number of substantially equidistantly spaced points of this marginal portion via micro-channels, which micro-channels run in a plane parallel to the longitudinal plane of the frame and are open at the upper side, which side is situated in one of the two outer planes of the frame that are parallel to the longitudinal plane of the said frame, when the electrode-element is not assembled and have substantially identical dimensions and a width b that is smaller than their depth d.

2. Apparatus according to claim 1, characterized in that b/d is at most 0.9.

3. Apparatus according to claim 1, characterized in that b/d is at most 0.5.

4. Apparatus according to any one of the claims 1-3, characterized in that the ratio between the hydraulic diameter H of the collecting channel and the hydraulic diameter h of the micro-channels is larger than 3.

5. Apparatus according to claim 4, characterized in that the ratio between the hydraulic diameter H of the collecting channel and the hydraulic diameter h of the micro-channels is larger than 5.

6. Electrode-element consisting of a flat electrode mounted in a frame, characterized in that said frame is provided with one or more apparatuses according to any one of the claims 1-5 for supplying and/or draining one or more fluids to and/or from one or more marginal portions of the flat electrode.

7. Electrode element according to claim 6, characterized in that said frame is made largely of thermoplastic material.

8. Fuel cell or battery consisting of a stack of elements, characterized in that one or more of these elements are electrode elements according to claim 6 or 7.

9. Apparatus according to one or more of the claims 1-5, as substantially described in the text and the figures.

Drawing